add explanations

src/Core/Hook/HookModuleFilter.php

@@ -26,6 +26,18 @@
 
 namespace PrestaShop\PrestaShop\Core\Hook;
 
+/**
+ * This service is responsible for filtering the list of modules for a given hook that is returned by
+ * the getHookModuleExecList method from Hook.php. It is called at the very end of getHookModuleExecList.
+ *
+ * How to use it to filter a list of modules for a hook:
+ *
+ * In your module, create a service which implements the HookModuleFilterInterface and give it
+ * the tag named core.hook_module_exec_filter. Then in your service, you can filter the list of modules
+ * in the filterHookModuleExecList method, according to your own logic.
+ *
+ * Your service will automatically be sent in this class's constructor, and be used to filter the list of modules.
+ */
 class HookModuleFilter implements HookModuleFilterInterface
 {
     private $hookModuleFilters;

src/Core/Hook/HookModuleFilterInterface.php

@@ -26,6 +26,10 @@
 
 namespace PrestaShop\PrestaShop\Core\Hook;
 
+/**
+ * This interface must be implemented by all services that will be used by the HookModuleFilter service.
+ * See HookModuleFilter.php for more explanations.
+ */
 interface HookModuleFilterInterface
 {
     public function filterHookModuleExecList(array $modules, string $hookName): array;